1. Field of the Invention
This invention relates to new and useful improvements in pumps and pump pistons for use in pumping mud or slush or slurries for petroleum well drilling apparatus, pipe line, mining and related industries. The invention is more particularly concerned with an improved piston for such applications having a means for circulating washing, cooling and lubricating liquids through the piston.
2. Brief Description of the Prior Art
In double acting pumps, the piston is flooded on both sides, as is the liner, with the fluid being pumped. In single acting pumps, only the working face of the piston is flooded, with the result that on the pressure stroke of the piston the surface temperature of the liner behind the piston may rise to levels that are injurious to the elastomeric seal when the piston returns on the back stroke, particularly in high speed operation.
In Lee U.S. Pat. No. 3,720,140, there is described and shown an improved single acting pump piston having an arrangement for circulating fluid to the piston during operation thereof to wash and cool the liner. This piston has the disadvantage that only the dead side of the piston is washed. There is no provision to wash the working side of the piston. There would be a substantial advantage in pumping abrasive materials if the pressure side of the piston could be washed free of those abrasives during normal operation.